The aims of this study were to evaluate the genetic diversity of the racing line Quarter Horse breed in Brazil and to provide data on the most influential ancestors by pedigree analysis. All horses that had participated in sprint races in Brazil between 1978 and 2016 were evaluated. There were 5,861 athletes horses (2,474 males and 3,387 females) born between 1971 and 2014. These animals were referred to as the racing population (Pr), which was divided into three subpopulations to evaluate three complete decades (84.5% of Pr). These subpopulations consisted of 1,712, 1,604 and 1,461 animals born in the 1980s (sP80), 1990s (sP90) and 2000s (sP00), respectively. The quality of the pedigree was assessed based on the number of complete equivalent generation traced. There were 5.4 (Pr), 4.7 (sP80), 5.7 (sP90) and 6.3 (sP00) generations, which permitted accuracy of the conclusions reported. The generation intervals were long, with 13.2 (sire-son/daughter) and 10.6 (dams-son/daughter) years (Pr). The coefficients of inbreeding and average relatedness were 0.95% and 1.84% for Pr and 1.60% and 2.56% for sP00, respectively. In Pr and sP00, the effective population size (N_e) based on ΔFi was 215 and 144, respectively, with 68 and 41 animals per generation. The probability of gene origin given by the effective number of founders (f_e), ancestors (f_a) and founder genome equivalents (f_ge) was 192, 61 and 34, respectively, for Pr, with considerable losses of genetic diversity over the last decades evaluated. The number of ancestors (founders or not) that explained the total genetic diversity was 1,587. This number is considered high; however, only 32 and 9 ancestors explained 50% of the genetic diversity of Pr and sP00, respectively. The 10 most influential ancestors of sP00 explained 52.2% of the total genetic diversity. The loss of genetic diversity and concentration in a reduced number of breeding animals indicate failures in the breeding and conservation programs of the racing line. Mating designs in conjunction with the selection of breeding animals should be promoted and goals should be defined for racing line of the Quarter Horse breed in Brazil.

这项研究的目的是评估巴西赛马季马品种的遗传多样性，并通过谱系分析提供有关最有影响力祖先的数据。评估了1978年至2016年在巴西参加短跑比赛的所有马匹。1971年至2014年之间出生的马匹有5,861匹（其中2,474头雄性和3,387头雌性）。这些动物被称为赛马种群（Pr），该种群被分为三个亚群以评估三个完整的十年（Pr的84.5％）。这些亚群分别由1980年代（sP80），1990年代（sP90）和2000年代（sP00）出生的1,712、1,604和1,461只动物组成。系谱的质量是基于所追踪的完全等价世代的数量进行评估的。有5.4（Pr），4.7（sP80），5.7（sP90）和6.3（sP00）世代，这使得所报告结论的准确性。世代间隔很长，分别为13.2年（父子/女儿）和10.6年（水坝/儿子/女儿）年（Pr）。Pr的近交系数和平均相关系数分别为Pr的0.95％和1.84％，而sP00的分别为1.60％和2.56％。在Pr和sP00中，有效种群数量（N基于ΔFi的_e）分别为215和144，每代有68和41只动物。由有效创始人（f _e），祖先（f _a）和创始人基因组等效物（f _ge）给出的基因起源概率）分别为192、61和34，而在过去的几十年中，Pr具有相当大的遗传多样性损失。能够解释整个遗传多样性的祖先（无论是否创立）的数量是1,587。这个数字被认为是很高的。然而，分别只有32和9个祖先解释了Pr和sP00的遗传多样性的50％。sP00的10个最有影响力的祖先解释了总遗传多样性的52.2％。数量减少的繁殖动物的遗传多样性和集中度的丧失表明，该赛鸽的繁殖和保护计划失败。应促进与配种动物的选择相配合的设计，并应为巴西“四分马”品种的赛马线设定目标。